Affiliation:
1. Saudi Aramco EXPEC ARC
Abstract
AbstractRe-injecting produced water is highly sought after to maintain reservoir pressure, preserve fresh water, and reduce water disposal costs. Produced water is often of low quality in terms of high total dissolved solids (TDS), inconsistent geochemical composition, bacteria content, and varying suspended solids and oil content. These factors pose a major formation damage risk if water re-injection into reservoirs is considered. The risks can be due to incompatibility with rocks (fines migration, permeability reduction, wettability alteration), the fluids (inorganic scale formation, emulsions), or the metal (Corrosion). Several water treatment processes exist to tailor such water into an acceptable injected fluid. The objective of this paper to provide an example analyzing produced water quality requirements and providing recommendations.Oil in water content in produced water was measured using Ultra-violet (UV) spectroscopy. Coreflood testing was conducted to assess damage in carbonate core plugs due to suspended oil and solids at 140°F. Environmental scanning electron microscope (ESEM) showed precipitation because of injecting produced water into carbonate core plugs.Re-injection of treated produced water can potentially cause reservoir damage due to combined effects of suspended oil, solids, and precipitation or scaling. The degree of reservoir damage is a function of oil/solids content, solid particle size, and scaling/precipitation potential. Oil/solid content and particle size in produced water should be reduced to lowest values that are economically feasible to achieve (e.g., total suspended solids (TSS) < 2 mg/L and total suspended oil (TSO) < 30-50 ppm. Well injection performance could be maintained through periodic flow back for routine clean-up, scheduled reservoir stimulations, and implementation of mentoring program at the water treatment plant and the wellhead to maintain water quality at a set threshold limit.